The present invention relates to an automatic door closer.
More particularly, it relates to a door closer with a closer shaft adapted to be connected to a door, and in which the closer shaft is turnably mounted in the region of the one end of an elongated housing in opposite directions from a position in which the door is closed. A cam disk is connected within the fluid-filled housing to the closer shaft for turning therewith, and this cam disk cooperates, by means of rollers fixed to a longitudinally movable slide, to move the latter in the longitudinal direction of the housing during turning of the door in either direction from the closed position. The slide is connected to a piston of a hydraulic damping arrangement and a spring arrangement forming an energy storage. The piston divides the interior of the housing into two pressure spaces which are connected to each other by channels for the throttled flow of the pressure medium from one pressure space, the volume of which is reduced during closing of the door, into the other pressure space.
With a door closer of the aforementioned type, which may be constructed as a closer mounted in an appropriate cavity in the floor, an automatic closing of the door will be obtained after each opening of the same, since the pressure medium can flow through the aforementioned channels from the pressure space, the volume of which is reduced during closing of the door, back into the other pressure space, in which the spring arrangement providing the closing force is arranged. This known door closer is provided forwardly and rearwardly of the piston with two channels, offset in the longitudinal direction of the housing, in which throttle devices are arranged through which the backflow speed of the pressure fluid from one pressure space into the other may be regulated. Thereby it is possible to dampen the first phase of the closer movement of the door to a lesser degree than the second phase of the door closing movement, so that the door will be moved without impact by the return spring to the closed position. During the opening movement of the door, the action of the throttle channels will be obviated by arranging a one-way valve in the piston which provides communication between the two pressure spaces during the closing movement of the door. However, the force of the closing spring must be overcome during the opening movement of the door. Especially at so-called fire doors which during existence of a fire have to be moved to a closed position, it is desirable that the door, during normal conditions, be easily movable, as a door without door closer, so that the door may be moved also by children without danger.
These objects are attained in a door closer disclosed in application Ser. No. 225,404, filed on Jan. 15, 1982.
The automatic door closer according to this application mainly comprises an elongated fluid-filled housing having a closed end and an opposite open end, a plug closing the open end of the housing, a first piston reciprocatably arranged in the housing and dividing the latter into a first pressure space adjacent the closed end of the housing and a second pressure space adjacent the plug, a closer shaft adapted to be connected to a door, extending transverse to the elongation of the housing and being turnably mounted in the housing in the region of the closed end, means connecting the closer shaft with the first piston for moving the latter, during the turning of the closer shaft in door-opening direction, in a first direction reducing the volume of the first pressure space but increasing the volume of the second pressure space, the piston-moving means comprising a piston rod slidably guided in the first piston and having a free end facing the plug, the plug being formed with a blind bore coaxial with the piston rod and having an open end facing the latter, spring means cooperating with the first piston for biasing the latter in a second direction opposite to the first direction, a second piston fixed to the free end of the piston rod and extending into the blind bore, first throttled passage means communicating at one end with the first pressure space and at the other end with a cylinder space formed between the closed end of the blind bore and the facing end of the second piston, second throttled passage means communicating at opposite ends respectively with the first and the second pressure space, and operator-controlled valve means in the second passage means movable between a closed position preventing flow of liquid through said second throttled passage means and an open position permitting flow through said second throttled passage means. The operator-controlled valve means is preferably an electromagnetically operated valve, and when the latter is moved to the closed position a pressure medium cushion will build up during the first opening of the door which will hold the first piston in the position it reaches at the end of the opening movement of the door, which will hold the first piston against the force of the spring means in the position thus arrived at. On the one hand, the door can then rest in any open position when the door is released, since the force of the closer spring is not acting. On the other hand, the door may be closed without exerting a relatively large force, since the second piston can be moved relative to the first one, and the pressure fluid has only to flow through the first throttled passage means, between the first pressure space and the cylinder space. Thus, in this construction the door closer function can, if desired, comp eliminated but retaining this function in case of danger, for instance during a fire, so that normally an easy opening and closing of the door by hand is possible.
In the above described door closer the second piston is fixed to the free end of the piston rod and moves together with the latter. This has the disadvantage that the seals of the first piston and the second piston are subjected to dynamic loads, and the construction is relatively difficult to manufacture and has a considerable length.